Ongoing technological developments have led to an increasing number of portable, battery-operated electronic products which in turn is generating a growing demand for energy efficient, low-power power supplies. Such products are either intrinsically low-powered or incorporate so-called “idle” or “sleep” modes of operation during which power consumption is reduced significantly compared to the power consumption of such products during their normal operating mode. Many such products generate multiple regulated direct current (DC) voltages derived from one common internal or external power source, such as a battery or a power adaptor, to comply with the power requirements of the products' internal subsystems. For example, a power supply voltage could have a voltage of 12 volts, however, an internal subsystem, e.g., a processor, might need only 2 volts. Two conventionally used devices for obtaining a desired voltage for an internal subsystem from a power supply are a step-down DC-DC power converter which is also known as a buck convertor, or a step-up DC-DC power converter which is also known as a boost converter.
The conventional buck converter 100 will now be described with respect to FIG. 1. The buck converter 100 includes a feedback amplifier 102, a finite state machine (FSM) 104, switch Sp 106, switch Sn 108, inductor 114 and a capacitor 116. Feedback amplifier 102 compares a sensed proportion of the output voltage, shown as Output Sense 110, with a reference voltage Vref 112 and provides a control input to the FSM 104 based upon the comparison. Based on the received control input, the FSM 104 drives switches Sp 106 and Sn 108. When switch Sp 106 is closed and switch Sn 108 is open, the input voltage Vdd 120 goes through the inductor 114 substantially without ohmic loss and charges capacitor 116. When switch Sp 106 is open and switch Sn 108 is closed, the buck converter 100 maintains a circulating charge to Ground 118. A typical example of an output voltage obtained from a conventional buck converter 100 can be Vout=1.2 Volts when the source voltage Vdd=5.5 Volts.
The conventional boost converter 200 will now be described with respect to FIG. 2. The boost converter 200 includes a feedback amplifier 202, a FSM 204, switch Sp 206, switch Sn 208, an inductor 210 and a capacitor 212. The feedback amplifier 202 compares a sensed proportion of the output voltage, shown as Output Sense 214, with a reference voltage Vref 216 and provides a control input to the FSM 204 based upon the comparison. Based on the received control input, the FSM 204 drives switches Sp 206 and Sn 208. When switch Sn 208 is closed and switch Sp 206 is open, the current flows from the input voltage Vdd 218 through inductor 210 to ground 220. The amount of the current and the correspondingly stored energy in the inductor 210 increases over the time for which Sn 208 remains closed. When switch Sn 208 is open and switch Sp 206 is closed, the energy stored in the inductor 210 can be transferred to the capacitor 212 and/or a load at the output 222 of the boost converter 200. A typical example of an output voltage obtained from a conventional boost converter 200 can be Vout=6.5 Volts when the source voltage Vdd 218 is 3.6 Volts.
In conventional designs of buck converters 100 and boost converters 200, as described above, each converter uses its own dedicated inductor 114, 210. Each inductor 114, 210 is relatively expensive and also occupies scarce circuit board real-estate. For applications which require multiple, regulated DC voltages derives from a common internal or external power source, such as a battery or a power adaptor, these cost and space issues can become aggravated.
Accordingly, systems and methods for improving the use of power converters which use inductors are desirable.